To the Editor:

After the establishment of the cystic fibrosis (CF) carrier screening protocol by the Israeli Society of Medical Geneticists in 2007, focused on the oriental Jews, and published in this journal, further data has been collected that led to updating the national protocol and this is reported now. The official recommendation for CF screening of the oriental Jews included three mutations: the 3121-1G>A, Y1092X, and 2751+insT in addition to the five known Ashkenazi mutations. The first two mutations were detected in 6.5 of 890 and 4 of 3474 screened alleles, leading to a carrier frequency of 0.23% and 1.46%, respectively. However, the 2751+insT mutation was not detected among 924 screened alleles although it was previously defined in 2 of 8 alleles derived from oriental patients with CF. Therefore, to increase the detection rate, this mutation was added to the initial recommended carrier screening panel. During the years 2007–2008, after the establishment of this protocol, further data has been collected that now justifies modification of the protocol (Table 1). Of 7618 newly studied oriental alleles, no mutation has been detected. This leads to a total of 8542 alleles studied during the whole screening period from 2006 (before the establishment of the formal screen) up to 2008. Furthermore, no patients carrying this mutation have been detected meanwhile. On the basis of this data, and because the results confer a carrier frequency <1:4000, this mutation is now excluded from the oriental CF mutation panel as recommended by the Israeli Society of Medical Geneticists, effective January 2009. This specific mutation exclusion complies with our strategy for dynamic modification of the Israeli genetic carrier screening according to new data gleaned from population studies of screened individuals.

Table 1 Allele frequency of the 2751+insT mutation
Full size table